1. Field
The present invention relates to a spacecraft, and more particularly, to a fault detector and a fault detection method for an attitude control system (ACS) of a spacecraft.
2. Description of the Related Art
In general, it is difficult for a ground control center to diagnose and detect faults of spacecrafts including satellites that orbit the earth, and space probes that explore the space outside of the earth's orbit. Therefore, the spacecraft requires a fault detection, isolation and recovery (FDIR) system installed therein.
In order for the spacecraft to stably carry out tasks thereof, an attitude of the spacecraft must be accurately controlled according to the tasks. The attitude of the spacecraft is controlled by an ACS installed in the spacecraft. The ACS installed in the spacecraft uses an attitude sensor that measures an attitude of the spacecraft and an actuator that changes the attitude of the spacecraft. For this reason, if the fault cannot be rapidly detected and isolated from the spacecraft upon occurrence of the fault in the sensor or actuator, the spacecraft cannot carry out the tasks.
A method of detecting a fault of the ACS of the spacecraft generally uses an interacting multiple model (IMM) estimation technique. FIG. 1 schematically shows a conventional actuator-fault detector using the IMM estimation technique, and FIG. 2 schematically shows a conventional sensor-fault detector using the IMM estimation technique.
Referring to FIG. 1, a conventional actuator-fault detector 10 includes a filter part 11 and a fault decision making part 12. The filter part 11 includes model filters corresponding to N fault types with respect to each of M actuators. Referring to FIG. 2, a conventional sensor-fault detector 20 includes a filter part 21 and a fault decision making part 22. The filter part 21 includes a first filter module 21a and a second filter module 21b corresponding to sensor modules, respectively. Each of the filter modules 21a and 21b includes L model filters corresponding to fault types.
As shown in FIGS. 1 and 2, since the conventional sensor- and actuator-fault detectors must have a large number of model filters to recognize the fault types, calculations must also be increased, thereby causing a reduction in fault detection performance. Thus, improvement thereof is required.